dimensionscollidefandomcom-20200214-history
Clone
Cloning is the generation of genetically identical organisms: each group of such organisms is a clone. Ever since Aldous Huxley's Brave New World, cloning and clones have been the subject both of science fiction and of serious public concern over their possible biotechnological applications. Before taking a paranoid view, however, it is worth noting that clones occur widely and naturally. Many plant varieties are propagated as clones (for instance by grafting) and the summer aphids preying upon them are asexually produced, genetically identical individuals — clones. Identical twins are clones, and the famous Dionne quintuplets born in Canada in 1934 represent a human clone of five people. Sexual reproduction involves a re-assortment of the genetic material from the two parents and hence the generation of new, genetically distinct individuals. In contrast to this, methods of asexual reproduction result in the production of genetically identical individuals. Bacteria, yeast, and the individual cells of multicellular organisms are able to reproduce asexually, and the products of such replication are clones. Thus, for instance, all the cells in a multicellular organism represent one clone derived from the fertilized egg. During the process of development, and indeed at later stages of life, there may be stably inherited restrictions on the use of the genetic material or new mutations which define new clonally-related groups of cells. The cells of malignant tumours, for instance, usually carry numbers of mutations which were not originally present in the normal cells of the individual; as these cancer cells progress newer mutations may arise so that several discernibly different clones of cells may be found. One question of interest would be whether all the cells arise from one single event — is the tumour a clone? This question may be addressed in individuals where there is already more than one distinguishable clone of cells present. In women, one of the two X chromosomes will have been inactivated early in development in a random but stable manner. This results in all the tissues being a mosaic of two alternative types of cell. Tumours typically display a single type, demonstrating their clonal origin from a single precursor cell. This illustrates another important aspect of cloning: the origin of the clone purifies it from a mixed population. For example, many cultivated plants are deliberately propagated asexually by cuttings or grafting, so that one particular variety may be maintained. In molecular biology, this property — that the isolation of a clone selects, maintains, and propagates as a single pure variant — is used directly for analysis of the genetic material itself; the DNA. Pieces of DNA are inserted into a bacterial or viral host in a form that replicates asexually. One single cell is used to start a colony — a clone — and thus large amounts of a single purified DNA fragment may be isolated. All the cells of a multicellular organism arising from one fertilized egg are clones and, unless subsequently modified, contain the same genetic information. This was demonstrated in plants by regeneration of a whole plant from a single cell from a carrot root. In animals it was shown possible to transplant the nucleus from a gut cell of a tadpole into a fertilized egg, which had had its own nucleus destroyed, and regenerate a new tadpole which now had the genetics of the donor nucleus. Such cloning was first attempted for mammals using mice, but this did not work with any nuclei other than those from the earliest embryos. In the 1990s, however, Ian Wilmut and a team at the Roslin Research Institute in Edinburgh demonstrated a technique allowing nuclei from cells in tissue culture to be used to clone a sheep. They have now demonstrated that these tissue culture cells can be derived from an adult sheep. The lamb (named Dolly), who was produced from a nucleus from a cell grown from the breast tissue of an adult sheep, has had major political impact as it is now clear that there is no theoretical reason why this cloning should not be possible not only with sheep but with other mammals, including humans. Cloning people is illegal in Britain, but world-wide legislation is not in place. In some quarters it is argued, however, that the technique per se might be useful to regenerate transplant tissues or organs without ever compromising the ethical, legal, and moral susceptibilities that would arise from deliberately generating whole fetuses or people. — Martin Evans See also biotechnology; stem cells. TopHome > Library > Religion & Spirituality > Buddhism Dictionary There is no ‘official’ Buddhist position on cloning nor is one likely to emerge since there is no central authority qualified to speak for the religion as a whole. Based on traditional teachings, however, the attitude of Buddhists in general towards recent advances in genetic engineering is likely to be one of caution. In particular, there are grounds for serious concern surrounding the technique of nucleus substitution. This is when the nucleus of a fertilized egg cell is extracted and replaced with the nucleus of a cell from another being in order to produce a twin of the mature animal, as in the case of Dolly the sheep in 1997. Buddhists are unlikely to have the same objections to the technique as Christians or other theistic religions. For Christians, to bring into being a new human or animal life by cloning may be seen as usurping the role of the creator. This is not a problem for Buddhism, because in Buddhism the creation of new life is not seen as a ‘gift from God’. For this reason the technique in itself would not be seen as problematic. Furthermore, although Buddhists understand sexual reproduction to be the overwhelmingly most common means by which humans and animals are reborn, it teaches that life can come into being through one of ‘four wombs’ (catur yoni). The last of these refers to the supernatural phenomenon of ‘spontaneous generation’ by which sages and supernatural beings have the power to materialize a human form. Life can thus legitimately begin in more ways than one. Although the technique of cloning may be morally neutral in itself, there are concerns surrounding the purposes for which it may be used. These centre on the fact that the nature of the technique leads life to be viewed as a product rather than an end in itself. The clone is produced by technicians in a laboratory, and for most of the purposes envisaged so far is then treated as an expendable resource rather than an individual with its own rights and intrinsic dignity. It is hard to see what purposes—scientific or otherwise—can justify the dehumanization that results when life is created and manipulated for other ends. For example, if the clone is to be used to provide spare organs for the person cloned, it would mean that individual life was being produced to be used as a mere instrument for the benefit of another, and effectively treated as property in the way slaves once were. Such dehumanizing techniques would be repugnant to Buddhism, which teaches that individual beings (both human and animal) are worthy of respect in their own right. Buddhism is more concerned about animals than some other religions, and so is likely to be more cautious about the use of animals in experiments of this kind. It should be remembered that Ian Wilmut, the creator of Dolly, failed 276 times before Dolly was conceived. Naturally, in the case of human beings a failure rate of this kind would be even graver, and when weighed against the benefits to be gained from human cloning identified so far the risks do not appear to be justified. In fact, there appears to be no single compelling reason for cloning human subjects. The benefits identified so far fall into two main groups: as an aid to current IVF techniques, and use for genetic selection or eugenics purposes. The numbers who would benefit from the first are very small, and history has shown the potentially grave consequences of the latter. See also Stem Cell Research; Medicine. TopHome > Library > Science > Science Q&A A clone is a group of cells derived from the original cell by fission (one cell dividing into two cells) or by mitosis (cell nucleus division with each chromosome splitting into two). It perpetuates an existing organism's genetic make-up. Gardeners have been making clones (copies) of plants for centuries by taking cuttings of plants to make genetically identical copies. For plants that refuse to grow from cuttings, or for the animal world, modern scientific techniques have greatly extended the range of cloning. The technique for plants starts with taking a cutting of a plant, usually the "best" one in terms of reproductivity or decorativeness or other standard. Since all the plant's cells contain the genetic information from which the entire plant can be reconstructed, the cutting can be taken from any part of the plant. Placed in a culture medium having nutritious chemicals and a growth hormone, the cells in the cutting divide, doubling in size every six weeks until the mass of cells produces small, white, globular points called embryoids. These embryoids develop roots, or shoots, and begin to look like tiny plants. Transplanted into compost, these plants grow into exact copies of the parent plant. The whole process takes 18 months. This process, called tissue culture, has been used to make clones of oil palm, asparagus, pineapples, strawberries, brussels sprouts, cauliflower, bananas, carnations, ferns, etc. Besides making high productive copies of the best plant available, this method controls viral diseases that are passed through seed generations. Category:Speices